Gas conversion process



D80 1963 H. G. ELLERT ETAL 3,

GAS CONVERSION PROCESS Filed June 21, 1960 2 Sheets-Sheet 1 l6\ I I8 l22 PRODUCT FIG.

Henry George Ellerr Charles Newton Kimberlin,Jr. Inventors By a Z 7 )75114 Attorney 3, 1963 H. ca. ELLERT ETAL 3,113,162

GAS CONVERSION PROCESS Filed June 21, 1960 2 Sheets-Sheet 2 Attorney 5 Im uE mE G N or. m mE mmma w wzwmomm: m :o :9: on J% J n o m W 29.25029:fiwm qmw 1m M m v H K E n 3 w? m E mm, m NI, t m 86mm 9% m n o m m 3mwwzmazoo y N9 55% J2EE 3 W665. on 6H B l QL 5m 5m 188E200 v 3. 6mm. BEmz8z= 596mm United States Patent 3,113,162 GAS CONVERSION PRQCESS HenryGeorge Ellert and Charles Newton Kimberiin, .Ir., Baton Rouge, La,assignors to Esso Research and Engineering Company, a corporation ofDelaware Filed June 21, 1960, Ser. No. 37,781 6 Claims. (Cl. 260-676)The present invention relates to the conversion of light hydrocarbongases, and in particular to hydrocarbon gases having no more than fourcarbon atoms, to valuable liquid hydrocarbons suitable as fuel andchemical intermediates. More particularly, the present invention relatesto the conversion of low molecular weight hydrocarbon gases to highermolecular weight valuable hydrocarbons in the presence of a hydrogenfluoride comprising catalyst. In a particular preferred embodiment, thepresent invention relates to the conversion of low molecular weightsaturated hydrocarbons such as butane into a liquid, non-aromatichydrocarbon product boiling in the heavy naphtha and middle distillaterange.

In Serial No. 856,392, filed December 1, 1959, of which the presentapplication is a continuation-in-part, it was disclosed that thetreatment of paraflinic hydrocarbons having five or more carbon atomswith hydrogen fluoride in the vapor phase at high temperatures and inthe further presence of a high surface area contacting agent, such asactivated carbon, resulted in good yields of a highly aromatic productboiling in the middle distillate range. Thus, light naphthas boiling inthe C /C range, heptane, dodecane and cetane, when treated with gaseousanhydrous HF in the vapor phase in the presence of activated carbon attemperatures of about 900 to 1000 F., all gave high yields of C -Calkylated aromatics. Under the same reaction conditions but in theabsence of the char, no reaction product was obtained.

It has now been found that when lower molecular weight hydrocarbons,i.e. butane and lower, are contacted under the same reaction conditionswith the same catalyst system, there is obtained in good yields a liquidhydrocarbon product having approximately the same number of carbon atomsas that obtained from the CH- feed streams but substantiallynon-aromatic.

The conversion of hydrocarbons with hydrogen fluoride is well known. Itis normally carried out in the liquid phase, either with aqueous oranhydrous acid and with or without catalyst promoter, such as BF to givea variety of products. In the vapor phase, however, little or noreaction occurs with light hydrocarbons of the nature specified.

It is, therefore, the principal object of the present invention to setforth a novel process for converting low molecular weight paraflinichydrocarbons into middle distillates in good yields and with littlesecondary reaction product.

It has now been found that these objectives may be achieved bycontacting hydrocarbon streams of the nature hitherto described in thevapor phase with vaporized hydrogen fluoride in the further presence ofa high surface but otherwise inert contacting agent at eleveatedtemperature. The reaction is carried out at a temperature of about 600to 1300 F. and 700 to 1200 F. or, preferably 750 to 1150 F., whenprocessing paraflinic feeds, and the preferred contacting agent is highsurface area char or other activated carbon. In the absence of the highsurface area support, substantially no reaction is obtained, while inthe presence of the carbon, good yields of middle distillate areobtained.

The distinction between this conversion technique and that of conversionby treating with liquid HF is best understood by considering theconversion of a butane stream.

It is well known, for example, that butane is isomerized by liquid HF.Thus, at about to 400 F. using from 0.5 to 5 weights of HF based onbutane feed, and under the developed pressure of the system, n-butane isconverted to a near thermodynamic distribution of the two isomers. Whilethe conversion is generally selective, overly severe process conditionscan lead to some cracking. The formation of trace amounts of tar, calledconjunct polymer and consisting of very high molecular weight, highlyunsaturated cyclic species, may accompany cracking conversion. Incontrast, vapor phase treatment of n-butane with HF in the presence of aporous contacting agent such as activated carbon (1) gives negligibleisomerization, (2) produces liquid hydrocarbons in good selectivity, (3)said liquid hydrocarbons consisting mainly of acyclic monoolefins whichare substantially lower in molecular weight and substantially lesshydrogen deficient than the conjunct polymer obtained in liquid phasetreatment.

Although any mixture of low molecular weight paraffinic hydrocarbonshaving no more than four carbon atoms may be employed, the presentinvention is most readily illustrated by showing the treatment of abutane stream. In the accompanying drawings, there is represented apreferred modification for carrying out the basic reaction in FIGURE 1,while FIGURE 2 is an embodiment designed to prepare high quality jet anddiesel fuel.

Turning now to FIGURE 1, a feed of the type described above is passedthrough line 2, vaporized in heater 4 and the heated vapor passed intoreaction vessel 6. Similarly, gaseous hydrogen fluoride is passed vialine 8 into reactor 6. The latter is packed with highly porous,non-reactive contacting agent, preferably activated carbon. Bynonreactive is meant those agents that will not react with HF. Besidescarbon, amorphous calcium fluoride, magnesium fluoride and similarcompositions may also be employed. The hydrogen fluoride to hydrocarbonfeed ratio is about 0.1 to 4.0, preferably 0.5 to 2. The liquid hourlyspace velocity is maintained at from 0.2 to 4.0 v./v., depending uponthe temperature and the acid to hydrocarbon ratio. The temperaturewithin reactor 6 may be from 600 to about 1300 F., and preferably 850 to1150 F. Pressure is atmospheric or slightly above.

The reaction mixture comprising reactants, catalyst and reactor productsis passed via line 10 to condensation vessel 12. Any low molecularweight hydrocarbon gases formed during the reaction as well as unreactedgases may be recycled to the reactor via line 14. This recycle has theeffect of decreasing dry gas make in the reaction. Similar eflfects maybe realized by recycling a portion of the desired hydrocarbon product.

The condensed product may then be passed to settler 18 via line 16. HFmay then be separated and recycled via line 20 and be revaporized.Alternately, only the liquid product is condensed, and the HF, gaseousproducts and unconverted feed are recycled as a gas stream. The desiredhydrocarbon product is recovered via line 22 and may be freed from acidcontaminants by washing, caustic scrubbing, and the like, followed by adistillation step.

The embodiment shown in FIGURE 2 is especially attractive for use inmany areas where light hydrocarbons are in over-supply while heavierfuels, particularly jet and diesel fuels, are in high demand. Inaccordance with this embodiment, the olefinic fuel produced in thereaction is subsequently hydrogenated, preferably in part at least bythe hydrogen formed during the reaction to improve the burningcharacteristics and produce a high quality, high density diesel or jetfuel.

Turning now to FIGURE 2, a light hydrocarbon feed is passed via line 30into reactor 32, packed with active carbon. Hydrogen fluoride isadmitted via line 58. Re-

action conditions within 32 are temperatures of 850 to 1200 F.,hydrocarbon space velocity of 0.5 to 2 v./v./hr., 0.1 to 2.0 HF/oilratio (weight) and a pressure of atmospheric to 400 p.s.i.g. Whenelevated pressures are employed, somewhat more severe reactionconditions are employed to offset the retarding effects of pressure onreaction rates. High pressures are, however, beneficial in anotherrespect as indicated below.

The reactor efiluent is then passed via line 34 to partial condenser 35where products heavier than the feed are Withdrawn via line 38 andpassed to hydrogenation zone 40. The remainder of the reactor efiiuentis withdrawn through line 42, condensed, and passed to settler 44.Unconverted feed and some lower hydrocarbons are recycled to reactor 32via line 47. A hydrogen-rich stream is withdrawn overhead from settler44 and, in the case of a previous high pressure operation in reactor 32,it is passed directly to hydrogenator 40 via lines 54 and 55. If a lowpressure operation is employed in 32, the hydrogen-rich stream may bepassed via line 48 to compressor for compression up to 200 to 400p.s.i.g. From settler 44 acid is recycled to the reactor via line 46.

The product from the reactor, which may boil in the range of 200 to 600F., is then recombined with the hydrogen at, for example, 200 to 400p.s.i.g. and 500 B, using a platinum catalyst, in hydrogenator 40, whichis of conventional design, and a high quality product boiling in thekerosene range is recovered. If desired or necessary, auxiliary orsupplementary hydrogen may be supplied through line 57.

Though the process has been described in connection with a fixed bed ofcontacting agent, the latter may be present in the form of a bed offinely divided fluidized solids or a moving bed. Furthermore, it may bedesirable to add a promoter to the active carbon. Suitable promoters aregroups II, III, and VIII metals, metal oxides and metal fluorides, inconcentration of 0.1 to 20 wt. percent of the carbon. Similarly, it maybe desirable to add promoters to the hydrogen fluoride, such as BF smallamounts of water or both.

The carbon gradually loses activity and selectivity with time, andreactivation is required. The latter may be accomplished by feedingsuperheated steam continually or intermittently to the carbon bed. Whilethis may be done in a single vessel system, best results are obtained ina two vessel system such as employed in con ventional fluid solidsunits. In this case, reaction is carried out in one vessel, regenerationin the other at somewhat higher than process temperatures, e.g. 1400 to1600 F., as against 900 to 1200 F.

The advantages of operating in accordance with the present invention maybe further seen and illustrated by the following specific examples.

The substantial unreactivity of hydrocarbons to vaporized HP in theabsence of a support, or in the pres ence of a support not having anactive surface, is shown in Example 1 below.

EXAMPLE 1 Packing Monel Gauze Copper Shot Temperature, F 962 951 HF/OilWt. Ratio 1.3 1. 5 Total v./v., hr 0. 7 0.8 Conversion, Wt. percent 5 5a a: Again negligible conversion was obtained and the recovered liquidwas essentially unconverted dodecane.

EXAMPLE 2 The utility of the process for upgrading and converting normalbutane into middle distillate is shown below.

(a) A mixture comprised of 1.11 weights of anhydrous HF and 1 weight ofn-butane is passed at 1100 F. and 612 total gas velocity through a bedof activated carbon. Butane conversion is 29.6% and the yield of liquidhydrocarbons is 11.4%. The liquid product consists mainly of C /Cacyclic monoolefins and is suitable for use as a distillate fuel or achemical intermediate. Other products are hydrogen and a mixture ofmethane and C /C olefins and paraffins. Only trace amounts of isobutaneare found in the product.

(12) While a range of temperatures may be employed, under reasonableconditions of holding time and HF/oil ratio, temperatures around 800 F.and below give impractically low conversions. For example, an HF/butanemixture (1.57 HF/CJ-I wt. ratio) is passed at 800 F. and 573 total gasvelocity through a bed of activated carbon. Conversion is only 2.0 wt.percent, the liquid product yield being 0.5 wt. percent.

(c) Holding time, as established by total gas space velocity, may bevaried over a wide range, though excessive holding time results indegradation of the liquid product. For example, at 1100 F. and 1.5HF/butane weight ratio, selectivity to liquid products is only 2.2 wt.percent at 36 v./hr./v. vs. 41.8 Wt. percent at 550 v./hr./v.

EXAMPLE 3 Autoclave treatment of butane with anhydrous, liquid HP (3HF/C H weight ratio, 225 F. for 2 hours) gives some isomerization, atrace amount of cracked products, but little if any heavier product. Todistinguish further vapor phase HF conversion in the presence ofactivated carbon from the liquid phase reaction, butane was treated withliquid HF promoted by BP In this experiment, 102 grams of butane and 304grams of liquid HF were sealed in a 1 liter autoclave. The autoclave wasthen pressured to 200 p.s.i.g. with BF and heated 2 hours at 225 F. Thedeveloped pressure was 1000 p.s.i.g. Even under these severe conditions,no liquid products similar to those formed in the vapor phase reactionwere isoiated. The products were isobutane, gas and a small amount (lessthan 1%) of tar.

EXAMPLE 4 Conversion of Propane to Liquid by HF Vapor-Activated CarbonCatalyst A mixture of propane and anhydrous HF (0.88 El /C 15 wt. ratio)was passed through a bed of activated carbon at 1100 F. and 1353 gaseoushourly space velocity (0.5 w./hr./w.). About 9% conversion resulted, andisopentane was obtained in 13.3% selectivity.

What is claimed is:

1. A process for converting parafiinic hydrocarbons consistingessentially of butane into higher liquid monoolefin hydrocarbons whichcomprises contacting said butane in the vapor phase in a conversion zoneat a temperature of from about 600 to about 1300 F. with vaporizedhydrogen fluoride in the presence of a high surface area contactingagent substantially inert to hydrogen fluoride.

2. A process for converting a hydrocarbon stream consisting essentiallyof paraflins having no more than four carbon atoms into middledistillate which comprises contacting a vaporized stream of saidhydrocarbon in a reaction zone with vaporized hydrogen fluoride at atemperature of about 600 to about 1300 F. and at pressures fromatmospheric to about 400 p.s.i.g. with high surface area activatedcarbon, and recovering a product comprising liquid acyclic hydrocarbons.

3. A process for converting propane into middle distillate whichcomprises contacting a vaporized stream consisting essentially ofpropane with gaseous anhydrous HF and activated carbon at a temperatureof about 700 to about 1200 F. and at pressures of about atmospheric upto about 400 p.s.i.g., in a reaction zone, and recovering a liquidproduct containing isopentane.

4. A process for converting butane into middle distillate whichcomprises contacting a vaporized stream consisting essentially of butanewith gaseous anhydrous HF and activated carbon at a temperature of about700 to about 1200 F. and at pressures of about atmospheric up to about400 p.s.i.g., in a reaction zone, producing hydrogen and liquid acyclicmonoolefins boiling in the middle distillate range and Withdrawing saidliquid monoolefins.

5. The process of claim 4 wherein a high quality middle distillate fuelis made by hydrogenating the liquid acyclic monoolefin product at leastin part With the hydrogen so produced to obtain a saturated middledistillate fuel boiling in the range of about 200600 F.

6. The process of claim 4 wherein the product comprises C C acyclicmonoolefins.

References Cited in the file of this patent UNITED STATES PATENTS2,063,133 Tropsch Dec. 8, 1936 2,216,372 Lyman et al Oct. 1, 19402,414,271 OKelly et al Jan. 14, 1947 2,546,930 Passins Mar. 27, 19513,023,157 Ellert et al Feb. 27, 1962

1. A PROCESS FOR CONVERTING PARAFFINIC HYDROCARBONS CONSISTINGESSENTIALLY OF BUTANE INTO HIGHER LIQUID MONOOLEFIN HYDROCARBONS WHICHCOMPRISES CONTACTING SAID BUTANE IN THE VAPOR PHASE IN A CONVERSION ZONEAT A TEMPERATURE OF FROM ABOUT 600* TO ABOUT 1300*F. WITH VAPORIZEDHYDROGEN FLUORIDE IN THE PRESENCE OF A HIGH SURFACE AREA CONTACTINGAGENT SUBSTANTIALLY INERT TO HYDROGEN FLUORIDE.